Brake light help

by bitterfitter Sun Mar 20, 2016 9:40 am

So I was replacing my brake light switch last height and noticed my brake lights don't work. Same with my hazard flashers. Now my turn signals work and all my tail lights too. I checked the fuse. Looks good. I traced power through the brake light switch and to the directional switch connector on the column. I am thinking this switch is the problem. Any thoughts if I am on the right track ?

by thatfnthing Mon Mar 21, 2016 9:26 am

FWIW, on the four terminal brake switch (assuming that's what you have), two terminals are normal-open (NO) and two are normal-closed (NC). When the brake pedal is not depressed, the NO ones flow no juice. These are for the brake lights. The NC ones flow 12V -- this would be for cruise control, but it can also be used for things like TC lockup and ABS. When the brake pedal is pressed, the two reverse their roles -- the NO ones now have juice and your brake lights come on, and the NC ones break contact and the cruise control is cancelled.

I just don't remember off hand which pair is which. Any chance you have them reversed? You can use a multimeter set to continuity and test each pair of terminals -- the NC ones will beep the meter and the NO ones won't.

If not, the next test would be to have someone press the brake pedal while you use a multimeter on the actual brake light housing to see if it gets 12V. If no, I would suspect either a bad switch or the wire is broken between the switch and the housing. If yes, you have a bad ground for the tail light housing (though your tail lights shouldn't work either), or perhaps the wrong bulb.

One last idea: the switch is adjustable for distance to the pedal shaft -- is it possible it's not close enough to the pedal shaft for the pedal to push it in?

by bitterfitter Mon Mar 21, 2016 9:36 am

I have the 4 post connector switch. It is new and tested. I get power through it and up to the directional harmonica connector. Just nothing coming out of this connector. I have ordered a new directional switch and I am going to try and plug it in and test before I install it.
Looks to like the problem is in this directional switch. I also have all new bulbs in the tail lights and running lights and directionals work.
Hoping it's the switch....

by bitterfitter Thu Mar 24, 2016 8:56 pm

So I fixed the hazard and brake lights.
I got my new turn signal switch today. Plugged it in a nothing. I figured I'd double check everything. I pulled the fuse and replaced it. As I pulled it the one metal end and the glass seperated and fell apart. The fuse would test fine and wasn't burned out in the center. I think it seperated at the end inside and would test but under load It was no good.

It turned out to be the fuse. Just glad I found it.

by pila Thu Mar 24, 2016 10:03 pm

Yup !! that's a trap a few of us have been into !! Very Happy

I've had circuit breakers in airplanes do the same
thing...OK until a load is put on them. Not to easy to diagnose most times...

by bitterfitter Thu Mar 24, 2016 10:10 pm

I should have replaced the fuse from the start. But it tested good and allowed power all the way to the turn switch. Now I know better ....

by Hs1973 Fri Mar 25, 2016 5:15 am

Been there myself. My brake light fuse would be ok when testing but would stop working when driving. I almost took a truck up the a.. Couse the brakelights would fail without warning. New fuses all over and its ok. Funny thing is it was a new fuse, but still faulty.

by thatfnthing Fri Mar 25, 2016 9:06 am

Glad you found it!

by 74Malibu383 Fri Mar 25, 2016 11:34 am

bitterfitter wrote:So I fixed the hazard and brake lights.
I got my new turn signal switch today. Plugged it in a nothing. I figured I'd double check everything. I pulled the fuse and replaced it. As I pulled it the one metal end and the glass seperated and fell apart. The fuse would test fine and wasn't burned out in the center. I think it seperated at the end inside and would test but under load It was no good.

It turned out to be the fuse. Just glad I found it.

Oh man, I feel for you. Glad you found it though.

I chased a couple of nasty gremlins that came back to the exact same faulty (tested fine) fuses. That's one of the reasons with this last update, I ripped out the factory harness and went with a Painless one.

by Hs1973 Fri Mar 25, 2016 1:41 pm

Me to. I Got a new wiring harness with new fusebox original style bought at the elcamino store. It was Pricey but worth it. Although that one fuse that was faulty even though it was new, gave me a little trouble. Im still happy that all wiring is new.

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